CI: Only run nightly multinode job in stackhpc repo

Author: markgoddard

.github/workflows/stackhpc-multinode-scheduled.yml

@@ -47,3 +47,4 @@ jobs:
       stackhpc_kayobe_config_previous_version: ${{ needs.generate-inputs.outputs.stackhpc_kayobe_config_previous_version }}
       enable_slack_alert: true
     secrets: inherit
+    if: github.repository == 'stackhpc/stackhpc-kayobe-config'